1. Field of the Invention
The present invention relates to a repeater line backup technology by an integrated services digital network (ISDN) line at the time of the failure of an inter-node repeater line, etc. in a network composed of connection nodes, such as ATM nodes, etc. where a high-speed data transfer is available.
2. Description of the Related Art
In a network composed of ATM nodes where a high-speed data transfer is available, communications between a variety of media terminals accommodated in the node are conducted through a high-speed inter-node repeater line.
Generally speaking, such a network has a repeater line backup function by an ISDN line to make possible the continuation of a communication with no interruption between terminals even at the time of a failure in an inter-node repeater line.
In an ATM switching system, since for a repeater line a high-speed circuit is used to make possible a high-speed data transfer, a high-speed bypass line is also required to set up a bypass line at the time of a failure in a repeater line. To secure this high-speed bypass line, a bulk transfer control to secure a required band by multiplexing the required number (1 to 24 channels) of B channels in an ISDN switching network is performed as shown in FIG. 1.
The required number of B channels varies depending on a band to be secured.
The ISDN backup control has the following problems.
When, for a bypass line, a plurality of ISDN lines are used in a node connected to a plurality of nodes, in order to effectively use the ISDN lines, one ISDN line corresponding to each repeater line is not installed, and the ISDN lines and B channels are dynamically shared. Furthermore, in this operation the plurality of ISDN lines are handled as a pilot, a pilot number is allocated and in each node of a network, control is performed based on only the pilot number. By adopting this method, both the constituent data of each node in the network and the procedures of the line selection can be simplified.
However, since in such an operation the selection of each ISDN line is left to the ISDN switching network side when a bulk transfer by the selection of the plurality of B channels is performed, there is a problem that a required band can often not be secured due to the shortage of B channels for each ISDN line.
To be more specific, for example, it is assumed that when in a node A of FIG. 2 two ISDN backup lines with 23 B channels each are prepared and a failure occurs in a repeater line, a node a connected to the node A performs a bulk transfer by using 6 B channels in a first ISDN backup line, a node b connected to the node A by using the remaining 16 B channels of the first ISDN backup line, a node d connected to the node. A by using 6 B channels of a second ISDN backup line and a node e connected to the node A by using the remaining 6 B channels of the second ISDN backup line. In this state, in order to connect a node c requiring a bulk transfer of 6 B channels, to the node A, a call has to be originated at the pilot number set for the two ISDN backup lines. In this case, without being conscious of the number of B channels required for the bulk transfer, the ISDN switching network simply judges that there are idle B channels in the first ISDN backup line (23 Bxe2x88x92(6 B+16 B) greater than 0), and terminates the call connection request for the pilot number of the node A from a node c, to the first ISDN backup line. However, in the first ISDN backup line, since 22 B (=6 B+16 B) channels are already occupied and there is only one idle B channel, the call connection request from the node c requiring the bulk transfer of 6 B channels is refused in the middle of the termination. As a result, although there are still 6 idle B channels in the second ISDN backup line, the call connection request from the node c to the node A fails.
In this way, when a plurality of ISDN backup lines are represented by a pilot number, there is a problem that available idle B channels of an other ISDN backup line can often not be used effectively due to the occupancy of B channels in a part of the ISDN backup lines, which is the first problem.
Next, as shown in problem 1, when ISDN lines and B channels are dynamically shared, a required band (number of B channels) can often not be secured due to the partial concentration of bypass line connections from terminals. In this case, there is a problem that a part of a band for the bypass lines is used in order every time a call is originated from the terminals, and after the entire band is occupied, all new calls are refused to be connected unconditionally regardless of the priority.
This invention is made in the background described above, and an object of the present invention is to solve problem 1 by implementing the optimum selection of both the number of channels and the interface (ISDN line) needed for a bulk transfer, and to solve problem 2 by implementing a call priority control according to a band for bypass lines.
The first aspect of the present invention comprises connection node apparatuses for controlling the securing of a backup line for a repeater line between the connection node apparatuses by connecting the connection node apparatuses with each other by an ISDN line being an integrated services digital network line in which a bulk transfer by using a plurality of B channels is performed.
A bypass line connection control unit selects an ISDN line for backup in which a bulk transfer by using a plurality of B channels is performed, out of a plurality of ISDN which can be set between the connection node apparatuses, by using a pilot function on an ISDN switching network side in which ISDN are switched over, and simultaneously exchanges the number (child number) of an ISDN to be selected between the connection node apparatuses as user-user information in the D channel message of the ISDN when the ISDN is selected.
A channel management unit selects the ISDN for backup in which a bulk transfer by using a plurality of B channels is performed, based on the numbers to be exchanged.
The configuration of the first aspect of the present invention further comprises a bypass connection control unit for exchanging the number of B channels to be transferred in bulk between connection node apparatuses as user-user information in the D channel message of an ISDN, wherein the channel management unit 303 can be configured to select the ISDN for backup in which a bulk transfer by using a plurality of B channels is performed, based on both numbers and the number of B channels to be exchanged.
According to the first aspect of the present invention, an ISDN line for backup in which a required bulk transfer can be secured, can be precisely and effectively selected by exchanging the line number of an ISDN circuit to be selected as user-user information in the D channel message of the ISDN line.
By exchanging the number of B channels to be transferred in bulk together with the line number, the more precise selection of an ISDN line becomes available.
The second aspect of the present invention presumes a connection node apparatus for performing a call control to control a call from a terminal connected to the connection node apparatus when the backup line of a repeater line between the connection node apparatuses is secured, by connecting the connection node apparatuses with each other by an ISDN line being an integrated services digital network line in which a bulk transfer by a plurality of B channels is performed.
A bypass line band management unit manages the band of an ISDN line.
A call control processor unit controls calls from each terminal based on both the band of the ISDN line and manages a priority for each terminal.
The range to be claimed of the present invention also includes all methods of realizing the same functions as those possessed by systems implemented by the first and second aspects of the connection node apparatus of the present invention described above.
According to the second aspect of the present invention, a call priority control according to a bypass line band can be realized by controlling calls from each terminal based on the band of both an ISDN line for backup and priority information for each terminal. As a result, the serviceability for users can be improved, and simultaneously the effective use of a bypass line band becomes available.